GHG EMISSIONS, URBAN MOBILITY, AND MORPHOLOGY ■ 113implement a BRT network in addition to the existing suburban rail network,
whereas in Gauteng suburban rail is carrying barely 8 percent of commuters, and
the great majority of low-income commuters rely on microbuses. Th e dispersion
of population in Gauteng is due in part to its history of apartheid. In the past
10 years, a very successful subsidized housing program has contributed to fur-
ther disperse low-income people in distant suburbs while signifi cantly attenu-
ating the extreme poverty created by apartheid. Th e comparison as seen on the
three-dimensional representation of population densities between the resulting
city structure of Gauteng and that of Jakarta is striking. A BRT is being planned
for the municipality of Johannesburg (one of the municipalities in the Gauteng
metropolitan region), but the current urban structure will make it diffi cult to
operate for a long time. In addition, the violent opposition of microbus opera-
tors is making the project politically diffi cult. A change in transit mode involves
a new equilibrium of transit types, which creates losers as well as winners. Th is
is not an easy process, even when the fi nal long-range outcome seems desirable
for all.
Th e structure of cities is path dependent. Once a city is dominantly polycen-
tric, it is nearly impossible to return to a monocentric structure. Monocentric
cities, by contrast, can become polycentric through the decay of their tradi-
tional center. Th e inability to adapt land-use regulations, to manage traffi c, and
to operate an effi cient transit system are the three main factors that explain the
decay of traditional CBDs.
Transport Strategies Need to Be Consistent with Cities’ Spatial
Structures
Findings concerning the relationship between urban spatial structures and
transit can be summarized as follows:
- Transit is effi cient when trips’ origins are dispersed but destinations are
concentrated. - Individual transport and microbuses are more effi cient when origin and
destinations of trips are both dispersed and for linked trips if amenities are
dispersed. - Mode shift toward transit will happen only if price and speed are competi-
tive with other modes. - Trips toward dense downtown areas (more than 150 people/ha) should be
prevalently made by transit. Failure to provide effi cient transit service to the
CBD and to regulate traffi c and parking would result in a dispersion of jobs
in suburban areas, making transit ineffi cient as a primary means of trans-
port in the long term.